Focalized intraluminal balloons

ABSTRACT

Disclosed is a focal balloon having at least one reference zone and a focal zone. In one embodiment, the reference zone and focal zone are inflatable to a first generally cylindrical profile at a first pressure. At a second, greater pressure, the focal section expands to a second, greater diameter, while the reference zone remains substantially at the first diameter. In an alternate embodiment, the focal zone and the reference zone are inflatable to their respective predetermined diameters at the inflation pressure, in the absence of constricting lesions or anatomical structures. Multiple lobed and drug delivery embodiments are also disclosed.

The present application is a continuation of application Ser. No.08/742,437 filed on Oct. 30, 1996, which is a continuation-in-part ofcopending application Ser. No. 08/640,533, which is acontinuation-in-part of copending application Ser. No. 08/572,783, thedisclosures of which are hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to catheters for insertion into a bodylumen. More particularly, the present invention relates to “focal”balloon dilatation catheters for use in the vascular system. As usedherein, “focal” balloons are balloons which focus or concentrateexpansive energy at one or more predetermined regions along the surfaceof the balloon.

Prior art vascular dilatation balloons on typical dilatation catheterstend to fall into one of two broad classes. Most are considerednoncompliant balloons, formed from a generally nondistensible materialsuch as polyethylene. The perceived advantage of the noncompliantballoons is that they exhibit a substantially uniform exterior inflatedprofile which remains substantially unchanged upon incremental increasesin inflation pressure. In theory, noncompliant balloons are advantageousbecause they allow the introduction of increased inflation pressure tobreak particularly calcified lesions, yet retain a predictable inflatedprofile so that damage to the surrounding native lumen is minimized.

Certain compliant balloons are also known in the art. A compliantballoon is one which is able to grow in diameter in response toincreased inflation pressure. One difficulty with compliant balloons,however, is that inflation within a difficult lesion can cause theballoon to inflate around the plaque to produce a generallyhourglass-shaped inflated profile. This can result in damage to thenative vessel adjacent the obstruction, while at the same time failingto sufficiently alleviate the stenosis.

In use, both the compliant and noncompliant balloons are generallyinflated within a vascular stenosis to a rated inflation pressure. Atthat pressure, the configuration of most balloons in an unrestrictedexpansion is cylindrical. The balloon may be subsequently inflated to ahigher inflation pressure if that is desirable in the clinician'sjudgment. However, the clinician has no effective way to assess theactual inflated diameter of the balloon in vivo based upon theunconstrained in vitro balloon specifications. The in vivo expansioncharacteristics of the balloon may track or deviate from the in vitrospecifications depending upon the morphology of the lesion and theappropriateness of the selected balloon size. The clinician may knowonly generally or not at all the degree of calcification of the lesion,the symmetry or asymmetry, whether the lesion is soft or resilient, orother variations which affect inflation. In applications where arelatively accurate inflated diameter is desired, such as in certaindilatations or in the implantation of tubular stents, the clinicianusing prior dilatation balloons thus may not have enough informationabout the dilatation characteristics of a particular lesion to optimizethe dilatation or stent implantation procedure.

Therefore, there exists a need in the art for a vascular dilatationcatheter with a balloon which is able to grow predictably in response toincreased inflation pressure, and the expansion of which the cliniciancan observe in real time in comparison to a known diameter reference.

SUMMARY OF THE INVENTION

There is provided in accordance with one aspect of the present inventiona balloon catheter comprising an elongate flexible tubular body and aninflatable balloon on the tubular body. A proximal segment, a centralsegment and a distal segment on the balloon are inflatable to a firstinflated diameter at a first inflation pressure, and the proximal anddistal segment expand to a second, greater inflated diameter at a secondgreater inflation pressure. The central segment of the balloon remainsat a diameter which is less than the second diameter, at the secondinflation pressure. In one embodiment, the balloon additionallycomprises at least one expansion limiting band on the central segment tolimit inflation of the central segment of the balloon. Preferably, theexpansion limiting band limits expansion of the central segment to nomore than about the first inflated diameter.

In accordance with another aspect of the present invention, there isprovided a method of treating a site in a body lumen. The methodcomprises the steps of providing a catheter of the type having anelongate flexible tubular body and a dilatation balloon on the body. Aproximal segment, a distal segment and a central segment of the balloonare inflatable to a first diameter at a first inflation pressure; andthe proximal and distal segments of the balloon are inflatable to asecond, greater diameter, at a second, greater inflation pressure. Thecentral segment remains substantially at the first diameter at saidsecond inflation pressure.

The catheter is positioned within a body lumen so that the balloon isadjacent a treatment site, and the balloon is inflated to the firstinflation pressure. At the first inflation pressure, the proximalsegment, the distal segment and the central segment are inflated to nomore than about the first inflation diameter, The balloon is thereafterinflated to a second inflation pressure so that the proximal and distalsegments are expanded to the second inflation diameter, while thecentral segment is simultaneously restrained against further materialradial expansion.

Optionally, the foregoing method comprises the additional step ofexpressing a therapeutic or diagnostic media from the central segment ofthe balloon to the site in the body lumen.

In accordance with a further aspect of the present invention, there isprovided a method of implanting a tubular graft within a body lumen. Themethod comprises providing an elongate flexible tubular body having aninflatable balloon thereon, the balloon inflatable to a first diameterat a first inflation pressure to produce a generally cylindrical balloonprofile, and proximal and distal portions of the balloon areadditionally inflatable to a second, larger diameter at a second,greater inflation pressure. An expandable tubular graft is positioned onthe balloon, and the balloon is thereafter positioned within a bodylumen adjacent a treatment site.

The balloon is inflated to the first inflation diameter to expand thetubular graft and thereafter inflation pressure is increased to thesecond inflation pressure such that the proximal and distal portions ofthe balloon inflate to the second, larger diameter, to further expandthe proximal and distal portions of the tubular graft.

Further features and advantages of the present invention will becomeapparent to one of skill in the art in view of the Detailed Descriptionof Preferred Embodiments which follows, when considered together withthe attached drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a preferred embodiment of a variablediameter inflation catheter of one aspect of the present invention, inthe second inflation configuration.

FIG. 2 is a partial cross-sectional view of a preferred embodiment ofthe variable diameter inflation catheter at a first inflation profile.

FIG. 3 is a partial cross-sectional view of a preferred embodiment ofthe variable diameter inflation catheter at a second inflation profile.

FIG. 4 is a schematic view of the embodiment of FIG. 1, shown in thefirst inflation configuration.

FIG. 5 illustrates a comparison of compliance curves between thereference zones and the focal zone as a function of increased inflationpressure in a differential compliance focal balloon of the presentinvention.

FIG. 6 is a schematic illustration of a balloon of the present inventionhaving a relatively thin wall in the focal section.

FIG. 7 is a cross sectional schematic illustration of a fixed focalballoon catheter of the present invention.

FIG. 8 is a cross sectional view through a dual layer balloon having acentral compliant zone thereon.

FIG. 9 is a cross sectional view as in FIG. 8, with the compliant zonein the expanded configuration.

FIG. 10 is a cross sectional schematic view of a balloon profile havinga focal zone and a tapered distal zone.

FIG. 11 is a schematic elevational view of a dual inflation lumencatheter.

FIG. 12 is a cross sectional view through a dual layer balloon having aunique inflation lumen for each layer.

FIG. 13 is a cross sectional view of a dual layer balloon as in FIG. 12,in the focalized configuration.

FIG. 14 is a cross sectional view through a balloon similar to that inFIG. 13, but with added delivery capability.

FIG. 15 is a cross sectional schematic illustration of a balloon havinga proximal and a distal lobe.

FIG. 16 is a cross sectional schematic illustration of a dual balloonconfiguration.

FIG. 17 is a cross sectional illustration of a dual lobed balloonadapted for delivery of media into the vessel.

FIG. 18 is a cross sectional view of a dual balloon catheter, configuredfor delivery of media into the vessel.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, there is disclosed a variable diameter inflationcatheter 10 in accordance with of one aspect of the present invention.Catheters embodying additional features known in the vascular dilatationart, such as implantable stents, drug delivery, perfusion and dilatationfeatures, or any combination of these features, can be used incombination with the focal balloon of the present invention as will bereadily apparent to one of skill in the art in view of the disclosureherein.

The catheter 10 generally comprises an elongate tubular body 12extending between a proximal control end 14 and a distal functional end16. The length of the tubular body 12 depends upon the desiredapplication. For example, lengths in the area of about 120 cm to about140 cm are typical for use in percutaneous transluminal coronaryangioplasty applications.

The tubular body 12 may be produced in accordance with any of a varietyof known techniques for manufacturing balloon-tipped catheter bodies,such as by extrusion of appropriate biocompatible plastic materials.Alternatively, at least a portion or all of the length of tubular body12 may comprise a spring coil, solid walled hypodermic needle tubing, orbraided reinforced wall, as is understood in the catheter and guide wirearts.

In general, tubular body 12, in accordance with the present invention,is provided with a generally circular cross-sectional configurationhaving an external diameter within the range of from about 0.03 inchesto about 0.065 inches. In accordance with one preferred embodiment ofthe invention, the tubular body 12 has an external diameter of about0.042 inches (3.2 f) throughout most of its length. Alternatively,generally triangular or oval cross-sectional configurations can also beused, as well as other non-circular configurations, depending upon thenumber of lumen extending through the catheter, the method ofmanufacture and the intended use.

In a catheter intended for peripheral vascular applications, the tubularbody 12 will typically have an outside diameter within the range of fromabout 0.039 inches to about 0.065 inches. In coronary vascularapplications, the tubular body 12 will typically have an outsidediameter within the range of from about 0.026 inches to about 0.045inches. Diameters outside of the preferred ranges may also be used,provided that the functional consequences of the diameter are acceptablefor the intended purpose of the catheter. For example, the lower limitof the diameter for tubular body 12 in a given application will be afunction of the number of fluid or other functional lumen, supportstructures and the like contained in the catheter, and the desiredstructural integrity.

Tubular body 12 must have sufficient structural integrity (e.g.,“pushability”) to permit the catheter to be advanced to distal arteriallocations without buckling or undesirable bending of the tubular body12. The ability of the body 12 to transmit torque may also be desirable,such as in embodiments having a drug delivery capability on less thanthe entire circumference of the delivery balloon. Larger diametersgenerally have sufficient internal flow properties and structuralintegrity, but reduce perfusion in the artery in which the catheter isplaced. Increased diameter catheter bodies also tend to exhibit reducedflexibility, which can be disadvantageous in applications requiringplacement of the distal end of the catheter in a remote vascularlocation. In addition, lesions requiring treatment are sometimes locatedin particularly small diameter arteries, necessitating the lowestpossible profile.

As illustrated schematically in FIG. 1, the distal end 16 of catheter 10is provided with at least one inflation balloon 18 having a variablediameter. The proximal end 14 of catheter 10 is provided with a manifold20 having a plurality of access ports, as is known in the art.Generally, manifold 20 is provided with a guide wire port 22 in an overthe wire embodiment and a balloon inflation port 24. Additional accessports are provided as needed, depending upon the functional capabilitiesof the catheter 10. The balloon 18 can also be mounted on a rapidexchange type catheter, in which the proximal guidewire port 22 would beunnecessary as is understood in the art. In a rapid exchange embodiment,the proximal guidewire access port is positioned along the length of thetubular body 12, such as between about 4 and about 20 cm from the distalend of the catheter.

Referring to FIGS. 2 and 3, the two-step inflation profile of theinflation balloon 18 is illustrated. In FIG. 2, the balloon 18 isillustrated at a first inflation profile, in which in an unconstrainedexpansion it exhibits a substantially cylindrical central workingprofile. The dimensions in FIG. 2 are exaggerated to illustrate aproximal segment 26 and a distal segment 28 which are axially separatedby a central focal segment 30. However, as will be understood by one ofordinary skill in the art, when the balloon 18 is inflated to the firstinflation profile, the exterior of the balloon 18 preferably exhibits asubstantially smooth cylindrical working profile.

In FIG. 3, the inflation balloon 18 is illustrated at a second inflationprofile. The proximal segment 26 and the distal segment 28 of theballoon are separated by the central focal segment 30 having a greaterdiameter. The configuration of FIG. 2 is achieved by inflating theballoon 18 to a first inflation pressure, while the configuration ofFIG. 3 is achieved by increasing the inflation pressure to a second,higher pressure as will be discussed below.

The details of one preferred embodiment of the variable diameterinflation catheter 10 are discussed with reference to FIGS. 2 and 3.Preferably, the tubular body 12 is provided with at least a guidewirelumen 32 extending all the way through the balloon 18, and an inflationlumen 34 extending into the proximal end of the balloon 18.

In the illustrated embodiment, an inner balloon 36 is disposed coaxiallywithin an outer balloon 38. A substantially nondistensible expansionlimiting band 40 is disposed in between the balloons 36 and 38 adjacenta proximal annular shoulder 42, to limit the radial expansion of theballoon 18. Similarly, a distal expansion limiting band 44 is disposedbetween the inner balloon 36 and outer balloon 38 adjacent a distalannular shoulder 46.

Expansion limiting bands 40 and 44 or other inflation limitingstructures can be provided in any of a variety of ways which will bewell-understood by one of skill in the art in view of the disclosureherein. For example, in one embodiment, the bands 40 and 44 eachcomprise a tubular section of polyester, each having an axial length ofabout 5 mm, a diameter of about 2.5 mm and a wall thickness of about0.0003 inches. Other generally nondistensible materials such as nylon,polyamide, Kevlar fiber, cross-linked polyethylene, polyethyleneterephthalate and others, may be utilized to accomplish theexpansion-limiting effect.

The expansion limiting characteristics can be achieved by the additionof a structure that is discrete from the balloon, or by modifying theexpansion properties of the balloon material itself. For example, theballoon can be provided with zones of differing wall thickness, or zoneshaving different levels of cross linking as will be discussed.

In general, the bands 40 and 44 must be of a sufficient thickness orstructural integrity for the particular material used to substantiallywithstand inflation under the pressures normally utilized in the contextof dilatation catheters. However, the bands 40 and 44 are preferablythin enough to provide a substantially smooth exterior surface of theballoon 18.

Preferably, as illustrated in FIGS. 2 and 3, the expansion-limitingbands 40 and 44 are sandwiched between the inner balloon 36 and theouter balloon 38. In alternative embodiments, the expansion-limitingbands 40 and 44 or other inflation limiting structures may be coated ormounted on the exterior surface of the balloon 18, the interior surfaceof the balloon 18 or within the wall of the balloon 18. Balloon 18 canbe provided with two or more layers as illustrated, or with only asingle layer as will be discussed.

The axial length of the bands 40 and 44 can be varied widely dependingupon the dimensions and the objectives of the catheter 10 as will beapparent to one of ordinary skill in the art. Further, the proximal band40 and distal band 44 need not be of similar lengths. In general,however, some examples of dimensions which are useful in the coronaryangioplasty dilatation environment are reproduced in Table 1 below, inwhich A represents the axial length of the balloon 18 between proximalshoulder 42 and distal shoulder 46, B represents the axial distancebetween distal shoulder 46 and transition point 48, and C represents theaxial length of the central focal segment 30. The dimensions of Table 1are exemplary only, and the present invention can be accomplished usinga wide variety of other dimensions as will be apparent to one of skillin the art. TABLE 1 A B C 20 mm 5 mm 10 mm 30 mm 5 mm 20 mm 40 mm 5-10mm   20-30 mm  

The catheter 10 illustrated in FIGS. 2 and 3 can be manufactured inaccordance with any of a variety of techniques which will be appreciatedby one of ordinary skill in the art in view of the disclosure herein. Inthe following disclosure, particular materials and dimensions will beused as an example only, and other dimensions and materials can beselected depending upon the desired characteristics of the finishedproduct.

In one particular method of manufacturing, a low density polyethyleneextrusion stock tube having an inside diameter of about 0.018 inches andan outside diameter of about 0.043 inches is used for the inner andouter balloons 36, 38.

The polyethylene stock tubing is cross-linked by exposure to an electronbeam in accordance with techniques well known in the art. A test segmentof the cross-linked stock tubing is free blown up to 3.0 mm in diameter.If the cross-linked stock tubing can be free blown to a diameter greaterthen 3.0 mm, the stock tubing is cross-linked again and retested untilthe desired free blow diameter is achieved.

The appropriately cross-linked stock tubing is then blown to a diameterof 2.5 mm within a teflon capture tube (not shown) which acts to moldthe balloon to its desired first inflation diameter. The teflon capturetube is a generally tubular body which has approximately the same insidediameter as the desired inflation diameter of the balloon. The tefloncapture tube is heated by any of a number of heating means such aselectric coils or a furnace to a temperature which is sufficient to moldthe balloon to the desired inflation diameter. In this case, thecross-linked polyethylene balloon is preferably heated to a temperatureof about 300° F. The teflon chamber is then cooled to a temperaturebelow the softening temperature of the balloon. Once cooled, the balloonis deflated and removed from the capture tube.

A section of inflation balloon material is thereafter stretched withapplication of heat to neck down the proximal and distal ends 37, 39 toa thickness of about 0.001 inches and a diameter which relativelyclosely fits the portion of the tubular catheter body 12 to which it isto be sealed.

The balloon is then attached to the tubular body 12 by any of a varietyof bonding techniques known to one of skill in the art such as solventbonding, thermal adhesive bonding or by heat shrinking/sealing. Thechoice of bonding techniques is dependent on the type of balloonmaterial and tubular body material used to form the catheter 10.

In one particular method of manufacture, inner balloon 36 and outerballoon 38 are attached to the catheter body 10. The proximal necked end37 of the inner balloon 36 is heat sealed around the catheter body 12.The distal necked end 39 of the inner balloon 36 is thereafter heatsealed around the distal end 16 of the catheter body 12. In general, thelength of the proximal end 37 and the distal end 39 of the inner balloon36 which is secured to the catheter body 12 is within the range of fromabout 3 mm to about 10 mm, however the proximal and distal balloonnecked ends 37, 39 are as long as necessary to accomplish theirfunctions as a proximal and distal seal.

Expansion limiting bands 40 and 44 are respectively positioned at theproximal segment 26 and the distal segment 28 of the inner balloon 36and may be bonded or otherwise secured to the inner balloon 36. Theouter balloon 38 is thereafter be mounted to the catheter body 12 in asimilar manner as the inner balloon 36, following “necking down” of theproximal and distal axial ends of the outer balloon 38 by axialstretching under the application of heat. The outer balloon 38 isadvanced axially over the inner balloon 36 and the expansion limitingbands 40 and 44. The outer balloon 38 may thereafter be bonded to theinner balloon 36, and to the expansion limiting bands 40 and 44 by anyof a variety of bonding techniques such as solvent bonding, thermaladhesive bonding or by heat sealing also depending on the type ofballoon material used. Alternatively, the expansion limiting bands aresimply entrapped between the balloons without any bonding or adhesion.

In a preferred embodiment, the inner balloon and the outer balloon 36,38 are both cross-linked polyethylene balloons which are difficult tobond together using conventional solvents. If sealing is desired, theinner balloon 38 and the outer balloon 38 are heat sealed together asdescribed below. In another embodiment, the inner balloon 36 and outerballoon 38 are secured together through the use of a UV-curableadhesive.

The inner balloon 36 and the outer balloon 38, once mounted to thecatheter body 12, can be heat sealed together in a heating chamber (notshown) such as a Teflon capture tube. Inner balloon 36 and outer balloon38 are inflated in the chamber until the inner balloon and the outerballoon inflate to the first inflation diameter. The heating chamber isheated by any of a number of heating means such as electric coils or afurnace to heat air to a temperature which is sufficient to bond the twoballoons 36, 38 together. In this case, the cross-linked polyethyleneballoons are preferably heated to a temperature of about 300° F. withinthe chamber which causes both balloons 36, 38 to seal together to form adouble walled variable diameter inflation balloon 18. The chamber isthen cooled to a temperature below the softening temperature of theinner and outer balloons 36 and 38. Once cooled, the variable diameterballoon 18 is deflated and the catheter 10 is removed from the chamber.

It will be apparent to one of skill in the art, that it is possible toattach the inner balloon 36 and the outer balloon 38 to the catheterbody 12 without adhesively bonding or otherwise securing the twoballoons together. In this case, the two balloons will respond to theapplied inflation pressure with the inner balloon 36 forcing the outerballoon 38 to simultaneously inflate both balloons 36, 38. The expansionlimiting bands 40 and 44 can be merely sandwiched between the innerballoon 36 and the outer balloon 38 and do not in this embodiment needto be bonded to either balloon.

The variable diameter balloon design of the present invention can alsobe accomplished with a single layer balloon or a double layer balloonwithout the inclusion of additional expansion limiting bands. This isaccomplished by decreasing the relative compliance of the zones of theballoon that are intended to remain at the first inflated diameter.Alternatively, the compliance of the focal section can be increasedrelative to that of the reference zones.

For example, polyethylene extrusion stock is cross-linked to 3.0 mm andblown into a mold of a diameter of about 2.5 mm as described above toform a balloon. Balloon stock can be crosslinked either before or aftermounting on the catheter, and in either the inflated or deflated state.The proximal and distal segments 26, 28 of the balloon on the catheter10 are masked such as with steel clamps or other masks known in the artto block electron beam penetration, leaving the central segment 30 ofthe balloon exposed. The central segment 30 of the balloon 18 is exposedagain to an electron beam source to be further cross-linked at the 2.5mm diameter. Balloons manufactured in this manner have been found toexhibit a relatively highly compliant central zone and relatively lesscomplaint axial end zones in a manner that achieves the two-stepdilatation as illustrated in FIGS. 2 and 3.

Single layer balloons having the differential compliancy characteristicsdescribed above can also be provided using other balloon materials suchas polyethylene terephthalate (PET). For example, a one piece singlelayer PET balloon can be provided with a thinner wall in the focalsection compared to the one or two reference sections of the balloon.FIG. 6 discloses a schematic illustration of a balloon 50 in accordancewith this aspect of the present invention. The balloon 50 defines aninterior space 51 for containing inflation media as is understood in theart. The balloon 50 generally comprises a distal neck portion 52 andproximal neck portion 54 for securing the balloon 50 to the catheter. Aworking length of the balloon 56 extends between proximal shoulder 55and distal shoulder 57.

The working length 56 of the balloon 50 is provided with a proximalreference zone 62 and a distal reference zone 58, separated by a focalzone 60. As has been discussed in connection with previous embodiments,the balloon 50 can alternately be provided with only a single referencezone either 58 or 62, together with the focal zone 60. Preferably,however, both proximal and distal reference zones 62 and 58 will beutilized with a central focal zone 60.

The thickness of at least a portion of the balloon wall in the area offocal zone 60 is thinner than the wall thickness in the reference zones62 and 58.

In one embodiment of the single wall focal balloon of the presentinvention, the balloon comprises PET. The balloon has a working lengthof about 20 mm, and the proximal and distal reference zones 62 and 58each have a length of about 5 mm. The focal zone 60 has a length ofabout 10 mm. The first inflated diameter at 8 ATM is about 3.0 mm, andthe focal section inflates in vitro to about 3.5 mm at 16 ATM. The wallthickness in the area of reference zones 62 and 58 is about 0.001inches, and the wall thickness in the area of focal zone 60 is about0.0007 inches.

Whether the balloon comprises PET or other balloon materials known inthe art, a thinner focal section compared to the thickness at thereference section can be provided using a variety of techniques. Forexample, the PET balloon can be exposed to heat and stretched in thecenter portion to provide a relatively thinner wall than the endreference portions. Alternatively, the balloon can be heated at its endsto shrink the balloon thereby increasing the thickness of the materialin the regions exposed to heat.

Thinning a portion of the wall of the balloon by stretching the materialcan be accomplished in any of a variety of ways that will be apparent tothose of skill in the art, in view of the disclosure herein. One methodof reducing the wall thickness in the region of the focal zone involvesan axial elongation of the tubular balloon stock under the applicationof heat. In general, the present inventor has found that the percentreduction in wall thickness is roughly equivalent to the percent axialelongation of the tubular stock. Thus, the tube stock is axiallyelongated a sufficient distance to achieve the desired reduction in wallthickness.

In one application of the invention, a molded PET balloon having a wallthickness of about 0.001 inches was axially elongated a sufficientdistance to reduce the focal zone thickness to about 0.0007 inches. Amolded PET balloon having a wall thickness of about 0.0008 inches wasaxially elongated by 40% to produce a wall thickness of about 0.0005inches.

In one application of the method of the invention, a length of tubularpolymeric stock is provided. The stock may be cut to a useful workinglength, such as 10-20 centimeters. Excess stock length following theelongation process will be trimmed prior to mounting of the balloon onthe catheter shaft as will be understood by those of skill in the art.

A 15 cm length of PET balloon tubing having a wall thickness of about0.0010 inches and an inflated outside diameter of about 3.0 mm wasclamped at or near each end in a device configured to apply an axiallystretching force to the tubing. Prior to closing one of the clamps, aneedle was advanced through the open end of the tubing so that thetubing can be pressurized following clamping. Following clamping, thetubing was inflated under a pressure of about 100 psi, and axial tensionin the area of about 1 lb. was applied.

The foregoing setup for a 3 mm balloon was accomplished inside of a 3 mmcapture tube. First and second aluminum heat sinks were thermallycoupled to the capture tube, and spaced about 5 mm apart. A hot airheater having a length of about 5 mm in the axial tube direction waspositioned in between the heat sinks and advanced towards the capturetube to heat the capture tube. The heat sinks assist in localizing theregion of the tubing stock which will be heated by the heater, as willbe understood by those of skill in the art.

Upon reaching a temperature of about 200° F., the tube stock begins tostretch under the axial tension. The axial length of travel of thestretching clamps is preferably limited to provide a predetermined limitfor the percentage axial elongation. In one application of theinvention, the 5 mm heated section grew to about 5 or 7 mm in axiallength following a 20%-40% increase in the distance between the clamps.Any of a variety of modification to the foregoing procedure can bereadily envisioned by those of skill in the art. For example, alternatesources of heat such as forced air heating, infra red, electrical coil,and others known in the art can be used. In addition, stretching can beaccomplished through any of a variety of physical setups, which can bereadily assembled by those of skill in the art. Stretching without theapplication of heat, such as by cold rolling or cold forming a portionof tubular stock may also provide an acceptable thinning of the balloonwall for certain types of balloon materials.

Subject to the pressure retention characteristics of bonds betweendissimilar balloon materials, the balloon can alternatively be providedwith a relatively more compliant material in a focal section, and arelatively less compliant material in a reference section. Balloonshaving a combination of materials having different compliancies can bemanufactured, for example, using two extrusion heads which alternatelydrive balloon material through a single orifice. Any of a variety ofmaterial pairs may be used, such as nylons of different hardness, PETand PE, and others that can be selected by those skilled in the art. Asa further alternative, the focal section can be formed from an entirelydifferent balloon which is positioned adjacent a single referenceballoon or positioned in between two reference balloons to produce aballoon having some of the characteristics of the focal balloon of thepresent invention.

Balloons 18 made in accordance with the design illustrated in FIGS. 2and 3 have been found to exhibit the inflation pressure profileillustrated in Table 2. TABLE 2 CENTRAL SEGMENT PROXIMAL AND DISTALPRESSURE DIAMETER SEGMENT DIAMETER  6 atm 2.5 mm 2.5 mm  7 atm 2.6 mm2.5 mm  8 atm 2.7 mm 2.5 mm  9 atm 2.8 mm 2.5 mm 10 atm 2.9 mm 2.6 mm 11atm 3.0 mm 2.6 mm 12 atm 3.1 mm 2.7 mm 13 atm 3.2 mm 2.7 mm 14 atm 3.2mm 2.7 mm

The inflation pressure profile of the variable diameter inflationballoon 18 illustrated in Table 2 provides an example of the manner inwhich a balloon 18 made in accordance with the foregoing method isinflated with the application of increased pressure. Initially, thecentral segment 30 and the proximal and distal segments 26, 28 of theballoon 18 inflate together in vitro as the pressure increases. When thepressure reaches 6 ATM, for example, the diameter of the proximal anddistal segments 26, 28 and the central segment 30 of the balloon allremain at about 2.5 mm. At 11 ATM, the diameter of the central segment30 of the balloon 18 has grown to about 3 mm while the proximal anddistal segments 26, 28 remained inflated to the first diameter ofapproximately 2.5 mm. The diameter of the central section 30 of theballoon 18 will continue to increase at least in vitro until the burstpressure of the balloon 18 is reached. In one prototype, the burstpressure was approximately 20 ATM at normal body temperature.

Both the first inflation diameter and the second inflation diameter canalso be varied depending upon the desired catheter characteristics aswill be understood by one of ordinary skill in the art. In a preferredembodiment, a first inflated diameter of the catheter for coronaryangioplasty applications is approximately 2.5 mm. Upon an increase ofpressure, this diameter grows to a second inflated diameter ofapproximately 3 mm in the central focal segment 30. In general, balloonscan be readily constructed having a difference between the firstinflation diameter and second inflation diameter anywhere within therange of from about 0.1 mm up to 1.0 mm or more, depending upon theelastic limits of the material from which the balloon was constructed.Typically, coronary angioplasty dilatation balloons will have a firstdiameter within the range of from about 1.5 mm to about 4.0 mm. Typicalballoons for use in peripheral vascular applications will have a firstinflation diameter within the range of from about 2 mm to about 10 mm.

Dilatation balloons can readily be constructed in accordance with thepresent invention in which entire length of the balloon from, forexample, proximal shoulder 42 to distal shoulder 46 (FIG. 2) is variablefrom a first inflated diameter to a second larger inflated diameter inresponse to increasing pressure. Alternatively, balloons in accordancewith the present invention can readily be constructed in which aproximal portion of the balloon is compliant so that it can grow inresponse to increased pressure, while a distal portion of the balloonhas a fixed inflated diameter. This configuration may be desirable, forexample, when the native vessel diameter is decreasing in the distalcatheter direction. Positioning the catheter so that the compliantportion is on the proximal (larger diameter) portion of the vessel mayminimize damage to the vessel wall in certain applications.Alternatively, the compliant segment can readily be positioned on thedistal end of the balloon with a substantially fixed inflated diametersegment on the proximal end of the balloon.

A variable diameter balloon 18 made in accordance with the foregoingdesigns has been found to benefit certain conventional percutaneoustransluminal coronary angioplasty (PTCA) procedures. In accordance withthe method of the present invention, the variable diameter balloon 18 ispercutaneously advanced and positioned such that the central segment 30of the balloon 18 is adjacent a vascular treatment site. Generally, thetreatment site is a stenosis such as due to a plaque or thrombus. Thevariable diameter balloon 18 is inflated to a first inflation profile tobegin dilation of the stenosis. Preferably, the first inflation profileis achieved by applying up to about 6 ATM of pressure to the balloon 18.At the first inflation profile, the entire balloon is inflated to theinner diameter of the vessel, thus restoring patency to the vascularlumen. In one embodiment, the variable diameter balloon 18 is inflatedto a first inflation diameter, of about 2.5 mm, at an inflation pressureof 6 ATM. The first inflation diameter is preferably about the nativediameter of the vessel.

As additional pressure is applied to the variable diameter balloon 18, asecond inflation profile is achieved wherein the central segment 30 ofthe balloon 18 expands beyond the diameter of the first inflationprofile to a second inflation diameter, while the proximal segment 26and the distal segment 28 remain at or substantially at the firstinflation diameter. As the pressure applied to the variable diameterballoon 18 increases, the diameter of the central segment 30 of theballoon 18 extends past the native diameter of the vessel to the secondinflation diameter. Utilizing this method, and depending upon theballoon size selected, the stenosis is compressed to a point which isbeyond the native diameter of the vessel. In a preferred embodiment, atan applied pressure of 11 ATM the diameter of the central segment 30 ofthe balloon 18 at the second inflation diameter is 3 mm and the diameterof the proximal end 26 and the distal end 28 at the first inflationdiameter is approximately 2.5 mm. Second inflation diameters in betweenthe first inflation diameter and the maximum inflation diameter can bereadily achieved by controlling inflation pressure, as illustrated forone embodiment in Table 2, above.

After the stenosis is compressed to or beyond the native diameter of thevessel, the balloon is evacuated and the catheter withdrawn.Alternatively, if desired, the pressure is reduced until the balloon 18resumes the first inflation profile. At this point, the balloon 18 maybe held at the first inflation diameter for short periods to continue tomaintain patency of the lumen if short term rebound is a concern. Thispost dilatation step is preferably accomplished using a catheter havingperfusion capabilities. Finally, the remaining pressure applied to theballoon 18 is reduced causing the variable diameter balloon 18 todeflate. The catheter is then extracted from the vessel utilizingconventional PTCA procedures.

The “focal” or “differential compliance” balloon of the presentinvention provides important real time diagnostic information about thelesion being treated. In a balloon having one or more noncompliant orsubstantially noncompliant zones such as proximal segment 26 and distalsegment 28 and a central focal segment 30, (FIG. 2) inflation within alesion will proceed through a series of discreet phases. The phases canbe visually differentiated by observing the balloon fluoroscopically andcomparing the apparent diameter of the central section with the diameterof the one or more substantially noncompliant zones. The substantiallynoncompliant zones may be considered reference zones for presentpurposes.

When the balloon 18 is inflated within a lesion, the reference zone willnormally be positioned proximally or distally of the lesion and thecentral zone will be centered within the lesion. As balloon inflationbegins, the overall balloon may take on a “dog bone” shape with thecentral portion radially inwardly restrained by the lesion. As inflationpressure is increased, the central section will tend to expand until theballoon has assumed an overall generally cylindrical profile. At acertain higher pressure, the balloon will focalize, such that thecentral region has reached its second, larger inflated diameter. Byobserving the first pressure at which the balloon assumes a generallycylindrical configuration and the second higher pressure at which theballoon focalizes, the clinician can learn important information aboutthe morphology of the lesion.

For example, in a balloon rated 3.0 mm at 6 atmospheres, the referencezone may grow to 3.2 mm at 11 atmospheres. The focal section will growto 3.0 mm at 6 atmospheres, and, in a healthy artery, should grow to 3.5mm at 11 atmospheres. If there has been no focalization at 11atmospheres, the clinician will know that the lesion is highly calcifiedor is otherwise highly resistant to expansion. The pressure can then begradually increased up to a maximum pressure which approaches the burstpressure, and the pressure at which focalization is finally visualizedwill reveal information about the degree of calcification or otherinformation about the lesion.

Thus, there is provided in accordance with the present invention amethod of obtaining characterizing information about a lesion. Thecharacterizing information is obtained by positioning a differentialcompliance balloon in the artery such that a central focal section ispositioned within the lesion. The balloon is inflated to a firstinflation pressure such that the balloon achieves a “dogbone”configuration with the lesion. The clinician preferably notes that firstpressure. The pressure is increased until the balloon achieves agenerally cylindrical exterior configuration. The pressure at which thesubstantially cylindrical configuration is achieved is preferably noted.The pressure in the balloon is increased further until focalization ofthe central section is achieved, and the focalization pressure is noted.One or more of the noted pressures may be compared to other informationconcerning the same patient or against reference data to assess thenature of the lesion. Since the balloon can be readily fluoroscopicallyvisualized, the clinician receives real time information about the sizeof the inflation balloon merely by visually comparing the focal sectionwith the reference section. If, at a particular pressure, the balloon is“straight across” (i.e. has not focalized) the clinician can look at thereference chart for the balloon or rely upon experience to assess thediameter of the vessel at the treatment site.

In accordance with another aspect of the present invention, there isprovided a method of interactive angioplasty using the differentialcompliance balloon of the present invention. In general, the interactiveangioplasty method involves inflating the balloon to a first inflationpressure, which should produce a first inflation profile for aparticular expected lesion morphology. If the profile of the balloon atthe first inflation pressure is different than the expected firstinflation profile, the clinician will know that the lesion morphologymay be different than anticipated. The clinician can thus responsivelychange the course of treatment, such as by removing the catheter andreplacing it with a different one.

For example, if a highly calcified or fibrotic lesion is expected andthe first inflation pressure produces a substantially cylindricalballoon rather than a dogbone shaped balloon, the clinician maydetermine that the balloon selected was too small or the lesion was notcalcified or fibrotic as expected. That balloon catheter may bewithdrawn and a catheter having a larger balloon thereafter positionedin the lesion. If the expected degree of inflation at the focal zone(compared, for example, to the reference zone) fails to occur at theexpected inflation pressure, the clinician may alternatively elect toincrease the inflation pressure, thereby exerting a greater force on thelesion.

Alternatively, lesion morphology information obtained by comparing theexpected inflation profile at a given pressure stage with the actualinflation profile may cause the clinician to seek alternate treatment,such as drug therapy, surgery, or other techniques that may be availableat the time. More rapid progression than expected from dogbone tocylindrical to focalized inflation may indicate the presence of softplacque or of a thrombosis, and measures can be taken in response tominimize the risk of over dilatation or embolization. These measures mayinclude drug therapy such as local administration of streptokinase orTPA, or other measures such as atherectomy, laser therapy or stenting.

One of the advantages of the interactive angioplasty of the presentinvention is that the clinician can alter the course of treatment duringthe procedure, in response to information obtained during the procedureabout lesion morphology or progression of the procedure. For example, ifthe balloon fails to focalize at the pressure previously expected toproduce focalization, depending upon other circumstances of the patient,the clinician may determine that further dilatation of the lesion willproduce an undesirable dissection of the artery, and a differenttreatment may be indicated. Alternatively, the clinician may elect tosimply increase the inflation pressure until focalization occurs, orsubstitute a different balloon having a different inflation diameter orcapable of sustaining a greater inflation pressure.

At each of the reference points identified previously herein, such asthe dogbone profile, the cylindrical profile, and the focalized profile,any deviation from the expected pressure to achieve that profile canthus be noted by the clinician and used to assess the course of furthertreatment. The interactive angioplasty method of the present inventioncan be accomplished both in the context of balloon dilatation and alsoin the context of implantation and or sizing of an intervascularprosthesis (stent).

Pressure response data for a series of exemplary balloons manufacturedin accordance with the present invention using techniques describedpreviously herein is provided in Table III below. The compliance curvesfor a reference zone and a focal zone of a differential complianceballoon rated for 3.5 mm at 6 atmospheres are illustrated in FIG. 5.TABLE III EFFECT OF INCREASED PRESSURE ON BALLOON DIAMETER Balloon 11ATM 14 ATM 16 ATM 3.0 mm Reference Zone 3.2 mm 3.2 mm 3.3 mm Focal Zone3.5 mm 3.5 mm 3.5-3.7 mm    3.5 mm Reference Zone 3.7 mm 3.7 mm 3.8 mmFocal Zone 4.0 mm 4.0 mm 4.0-4.2 mm    4.0 mm Reference Zone 4.2 mm 4.2mm 4.3 mm Focal Zone 4.5 mm 4.5 mm 4.5-4.7 mm   

As exemplified in Table III, the reference zones on a particular balloonare expected to have a predetermined diameter at certain pressures. Forexample, the reference zones on a 3.0 mm balloon are expected to inflateto 3.2 mm at 11 ATM. If the balloon appears to be “straight across” at11 ATM, the clinician knows that the focal section and therefore thelesion has been inflated to 3.2 mm. If the balloon has focalized, theclinician knows that the lesion has been inflated to 3.5 mm by referringto a look up table containing the balloon specifications. Iffocalization does not occur until a higher pressure such as 14 ATM hasbeen reached, the clinician still knows that the lesion has beeninflated to 3.5 mm, but also knows that the lesion was relativelycalcified or fibrotic.

The present interactive angioplasty invention thus enables the clinicianto take into account the difference in balloon inflation characteristicsbetween the in vitro and in vivo environments. Balloons in vitro exhibita predictable inflation response to pressure. Balloon inflation in vivo,however, can be quite different from the balloon rating, and also fromlesion to lesion, as a result of the differences in vessel wallthickness, lesion morphology and other characteristics that affect theresistance to radial expansion in the area of the target lesion. Byproviding reference information such as the inflated diameter of thereference and focal zones of a balloon at each of a series of pressures,the clinician can determine the actual diameter of the balloon in thefocal zone by observing the balloon in either of the “straight across”or focalized inflation profiles.

The differential compliance balloon of the present invention is alsoparticularly suited for the implantation and or sizing of intravascularstents. For example, in a 3.2 mm vessel, it may be desirable to dilate astent to 3.5 mm inside diameter since some stents tend to recoil invivo. If the balloon is inflated up to 10 ATM with no focalization, theclinician knows to increase the pressure until a focal section becomesapparent. When the focal section has become apparent, the clinician willknow that the inside diameter of the stent has been appropriatelyinflated to 3.5 mm.

In accordance with a further aspect of the present invention, there isprovided a method of implanting a tubular stent within a body lumen.Tubular stents of the type adapted to be carried to a vascular site on aballoon catheter, and for expansion from a first insertion diameter to asecond implanted diameter are well-known in the art.

In accordance with the method of implanting a tubular stent, anexpandable stent is positioned about the deflated balloon of a variablediameter balloon catheter in accordance with the present invention. Theballoon is thereafter percutaneously inserted into the vascular systemand transluminally advanced to position the stent at the treatment site.The balloon is thereafter inflated to at least a first inflationconfiguration, wherein the balloon exhibits a substantially cylindricalprofile throughout its axial length. Thereafter, the balloon isoptionally inflated to a second inflation profile, thereby inflating atleast a portion of the stent to a second, greater diameter. Dependingupon the etiology of the underlying condition, the central region of thestent may preferentially be inflated to a larger diameter than either ofthe axial ends of the stent. Alternatively, the axial length of thestent is selected to approximately equal the axial length of the focalzone on the inflation balloon. In this manner, the inflation balloonwithin the stent is expandable to a diameter slightly larger than thenative diameter of the adjacent vessel. This permits subsequentovergrowth of endothelium along the interior wall of the stent whilestill leaving a lumen having an interior diameter within the stentapproximately equal to the native diameter of the lumen adjacent thestent.

In accordance with a further aspect of the present invention, thevariable diameter balloon is utilized to “tack down” a previouslypositioned tubular stent. In accordance with this aspect of the presentinvention, a tubular stent is identified within a body lumen. The focalballoon is positioned within the stent in accordance with conventionalPTCA procedures, and the balloon is inflated so that the central, focalsection enlarges the diameter of at least a first portion of the stent.The balloon is thereafter reduced in diameter, and, preferably,repositioned within a second region within the stent and then reinflatedto expand at least the second region of the stent. Expansions of thistype can be repeated until the stent has been expanded as desired. Theballoon is thereafter evacuated and removed from the patient.

In accordance with a further aspect of the present invention, there isprovided a method of percutaneous transluminal angioplasty in whichmultiple lesions of differing sizes are dilated without removing thecatheter from the body. In accordance with this aspect of the presentinvention, the variable diameter balloon is positioned within a firststenosis in accordance with conventional PTCA techniques. The balloon isdilated to a sufficient diameter to restore patency to the vascularlumen. The balloon is thereafter deflated, and repositioned within asecond stenosis in the vascular system. The balloon is inflated torestore patency of the vessel in the region of the second stenosis.Optionally, the balloon may be deflated, and repositioned within a thirdstenosis in the body lumen. The balloon is then inflated to a sufficientdiameter to restore patency in the body lumen in the region of the thirdstenosis. Four or more lesions can be treated seriatim in this manner.

Preferably, the balloon is inflated to a first diameter in the firststenosis, and to a second, different diameter, in the second stenosis.In this manner, multiple dilatations at different diameters can beaccomplished utilizing the balloon of the present invention. This methodis accomplished by supplying a first inflation pressure to the balloonwhile the balloon is positioned in a first position in the vascularsystem, and thereafter supplying a second pressure to the balloon whenthe balloon is in a second position in the vascular system. Inaccordance with the previous disclosure herein, each of the first andsecond inflation pressures is selected to achieve a preselectedinflation diameter of the balloon.

A number of the advantages of the interactive angioplasty methods andstent implantation and sizing methods of the present invention can alsobe accrued through the use of an alternate embodiment of the balloon ofthe present invention as illustrated in FIG. 7. Referring to FIG. 7,there is disclosed a fixed focal balloon 64. By “fixed” focal balloon,it is meant that the balloon assumes a stepped configuration in itsinitial in vitro inflated profile. Increased inflation pressure beyondthe pressure necessary to achieve the initial stepped inflation profiledoes not appreciably change the relative proportionality of the profilefrom its initial stepped configuration.

The stepped configuration is characterized by a difference in diameterbetween at least one reference zone and a focal zone, preferably on thesame balloon. The fixed focal balloon of the present invention can beconstructed using either relatively compliant or relatively noncompliantmaterials, with the resulting characteristics that will be readilyapparent to those of skill in the art in view of the disclosure herein.Preferably, the fixed focal balloon comprises polyethyleneterephthalate.

The embodiment of the fixed focal balloon 64 illustrated in FIG. 7 has acentral focal zone and a proximal as well as a distal reference zone.However, the present inventors also contemplate fixed focal balloons inwhich either the proximal reference zone or the distal reference zone isomitted. These embodiments include only a single reference zone and asingle focal zone. The reference zone may be positioned eitherproximally or distally of the focal zone.

For example, in one two segment embodiment of the present invention, aproximal segment on the balloon is inflatable to a greater diameter thana distal segment. In general, the proximal segment will inflate to agenerally cylindrical configuration in an unconstrained inflation. Atransition zone is disposed at the distal end of the proximal segment.In the transition zone, the diameter of the balloon steps down to thesmaller inflated diameter of the distal segment. The axial lengths anddiameters of the proximal and distal segments can vary widely dependingupon the intended use of the balloon. In one application, the balloon isused to size or implant two stents positioned end to end in a vessel.The stents may comprise a pair of 15 mm length stents or 20 mm lengthstents or otherwise as may be desired. For this application, the balloonmay have an overall length of from about 20 mm or 30 mm to about 40 mmor greater. In one 30 mm balloon, a proximal segment is approximately 15mm long and has an inflated diameter of about 3.5 mm. At the distal endof the proximal segment is a transition zone which will be generally beless than 1 or 2 mm in length and preferably about a ½ mm in length.Distally of the transition zone is a second segment approximately 15 mmin length and having an inflated diameter of about 3.0 mm. Alternatepairs of proximal and distal segment inflated diameters may also beutilized as will be appreciated by those of skill in the art. Ingeneral, the difference in diameter between the proximal and distalsegments will be within the range of from about 0.2 mm to about 1 mm,and, preferably, will be about 0.5 mm. Proximal and distal segmentdiameter and pairs for balloons believed useful by the present inventorinclude 4.0/3.5 mm, 3.5/3.0 mm, 3.0/2.5 mm. Proximal and distal balloonzone lengths are preferably approximately equal in a given balloon,e.g., 20 mm/20 mm in a 40 mm balloon, although dissimilar zone lengthsmay be desirable in particular specialty applications.

As a further alternative, the balloon is provided with three steppeddiameters in the inflated profile. In a 30 mm balloon, for example, aproximal 10 mm section inflates to a first diameter, an intermediate 10mm section inflates to a second diameter and a third 10 mm sectioninflates to a third diameter. Preferably, the first, second and thirddiameters decrease in the distal direction. The diameters of adjacentsections may be separated by 0.5 mm, 0.25 mm, or other differential asmay desired for the intended application. Thus, in an exemplary balloon,the first diameter is 3.5 mm, the second diameter is 3.0 mm and thethird diameter is 2.5 mm. In an alternate example, the first diameter is3.5 mm, the second diameter is 3.25 mm and the third diameter is 3.0 mm.Similar gradations from about 2 mm up through about 4.5 mm for coronaryapplications, and up to 8 or more millimeters for other applications maybe used.

Any of the preceding multizone balloons, particularly the two zone andthree zone balloons can be utilized to implant or size a single “long”stent or expandable graft. For present purposes, long stents will havean axial length of greater than about 20 mm, and could have any of avariety of lengths such as 25, 30, 35, 40, 45, 50, 55, 60 mm or longer.Corresponding balloon lengths are also contemplated. Stent and balloonlengths intermediate the foregoing dimensions may also be utilized, aswill be appreciated by those of skill in the art. Two or three or fouror more axially adjacent stents may also be implanted or sized using thecatheters described herein.

Any of the balloon catheter designs described herein may be utilized inthe method of implanting a tubular stent, the method of sizing apreviously implanted stent, or simultaneously implanting and sizingtubular stents (which term is intended to include grafts throughout).The balloon catheters disclosed herein are also useful in the methods ofsimultaneously implanting and/or sizing multiple stents.

Alternatively, the proximal and distal zones in a three zone balloon maybe inflatable to the relatively larger diameter, while the central zoneis inflated to the smaller, reference diameter. This embodiment may beconsidered to have a proximal and a distal focal zone and a singlecentral reference zone. These and additional variations are illustratedin FIGS. 8-18, discussed infra. The desirability of one combination overanother will be governed by the requirements for a particular balloondilatation or stent or graft implantation procedure as will be apparentto those of skill in the art in view of the disclosure herein.

Referring to the embodiment illustrated in FIG. 7, the fixed focalballoon 64 is provided with a proximal reference zone 66, a centralfocal zone 68 and a distal reference zone 70. The relative lengths ofeach of these zones may vary considerably depending upon the intendeduse of the balloon. In general, any of the dimensions of the balloon,both in terms of diameters and lengths as well as other catheterdimensions, may be the same as those disclosed in connection with otherembodiments previously disclosed herein. In one particular application,the focal zone 68 has an axial length of 10 millimeters, and each of theproximal zone 66 and distal zone 70 has an axial length of about 5millimeters. At 8 atmospheres inflation pressure, the proximal referencezone 66 has an outside diameter of about 3 millimeters, and the focalzone 68 has an outside diameter of about 3.4 millimeters. The sameballoon at 18 atmospheres inflation pressure has an outside diameter ofabout 3.1 millimeters in the proximal reference zone 66 and an outsidediameter of about 3.5 millimeters in the focal zone 68. That particularballoon was constructed from PET, having a wall thickness of about0.0006-0.0008 inches.

Depending upon the desired clinical performance of the balloon, therelative expansion characteristics of the reference zone compared to thefocal zone can be varied. For example, although the focal section willnormally retain a larger inflated diameter than the reference zone, thereference zone may grow in response to an increase in inflation pressurea greater amount than the focal zone. In one PET balloon, having a wallthickness in the range of from about 0.0006 to about 0.0008 inches, thegrowth of the reference zone upon an increase in inflation pressure from8 to 18 atmospheres was about 0.2610 millimeters. The growth in thefocal zone over the same pressure increase was about 0.1457 millimeters.It may alternatively be desired to achieve a greater growth in the focalzone compared to the reference zone, or an equal growth in each zone asa function of increased pressure. Optimizing the growth response toincreased pressure of the focal zone relative to the reference zone forany particular intended application can be accomplished by the exerciseof routine skill in the art in view of the disclosure therein.

The fixed focal balloon 64 further comprises a first transition 72 whichsteps the diameter of the balloon up from the diameter of the cathetershaft 74 to the diameter of the proximal reference zone 66. All balloonshave some form of transition, such as first transition 72, and thereference zone 66 is to be distinguished from what is simply atransition, such as transition 72. Thus, the reference zone 66 isprovided with a visibly discernable generally cylindrical exteriorconfiguration in the inflated state, or other characteristic inflatedconfiguration, so that it can be distinguished visibly from thetransition 72 in vivo. Thus, the proximal reference zone 66 can beeither a cylindrical section which transitions sharply into a generallyconical transition section, such as first transition 72. Alternatively,the reference zone 66 may comprise a continuation of a first transition72, but with a visibly different angle with respect to the longitudinalaxis of the catheter when compared to the angle of the surface of thefirst transition 72 taken in the axial direction. In one embodiment ofthe invention, the surface of the first transition 72 measured in theaxial direction lies at an angle of approximately 20 degrees withrespect to the longitudinal axis of the catheter shaft 74.

A second transition 76 is provided to step the diameter of the inflatedballoon from that of the proximal reference zone 66 to the focal zone68. A third transition 78 is provided to step the outside diameter ofthe inflated balloon from the diameter of focal zone 68 down to thediameter of distal reference zone 70. The angle of each of the secondand third transition sections can vary depending upon desiredperformance and design characteristics, but in one embodiment of theinvention have a surface which lies on a plane extending in the axialdirection at an angle of about 11° from the longitudinal axis of thecatheter shaft 74. The axial length of each of the second transition 76and third transition 78 will vary depending upon the difference indiameter of the focal zone from the reference zone, but will generallybe within the range of from about 0.5 mm to about 4 mm.

A fourth transition 80 is provided to step the diameter of the balloon64 from that of the distal reference zone 70 back down to the diameterof the distal catheter shaft or tip 82.

The three zone embodiment illustrated in FIG. 7 can be produced havingany of a variety of dimensions, depending upon the particularcontemplated end use of the catheter. In the following nonlimitingexamples of balloon dimensions, the dimensions for the balloon arerecited at 8 atmospheres inflation pressure in an unrestrained (invitro) expansion.

For example, balloons can be readily provided having a focal zone 68inflatable to an initial inflation diameter of anywhere within the rangefrom about 1.5 mm to about 10 mm. For coronary vascular applications,the focal zone will normally be inflatable to a diameter within therange from about 1.5 mm to about 4 mm, with balloons available at every0.25 mm increment in between.

The reference zone, such as proximal reference zone 66 and/or distalreference zone 70 is preferably inflatable to a diameter within therange from about 1.25 mm to about 9.5 mm. For coronary vascularapplications, the reference zone is preferably inflatable to a diameterwithin the range of from about 1.25 mm to about 3.5 mm.

The focal zone is normally inflatable to a generally cylindricalprofile, which has a diameter that is greater than the diameter in thereference zone. Neither the focal zone nor the reference zone or zonesneed to be precisely cylindrical. Thus, the present invention can stillbe accomplished with some slight curvature or bowing of the surface ofthe focal zone or reference zone taken along the axial direction.

In general, the maximum diameter of the focal zone will be within therange of from about 7% to about 30% percent or more greater than theaverage diameter of the reference zone. Preferably, the maximum diameterin the focal zone will be at least about 10% greater than the averagediameter in the reference zone.

The configuration of the reference zone compared to the focal zone canbe varied considerably, as long as the reference zone and the focal zoneouter diameters can be visualized by the clinician using conventionalfluoroscopic or other visualization techniques. Thus, although thereference zone can take on a slightly conical configuration such that itramps radially outwardly in the direction of the focal zone, it shouldnot be to such an extent that the clinician cannot visuallydifferentiate the inflation profile of the focal zone compared to thereference zone in vivo.

The function of the reference zone, to provide a visual reference toindicate the relative inflation of the focal zone, can be accomplishedby the provision of radio opaque markers at either end of or within theballoon. For example, inflatable or flexible radio opaque markers may beprovided along the transition in a balloon from the catheter shaft tothe working zone in an appropriate position along the ramp such that,when the balloon is inflated, the radio opaque marker provides a visualindication of a predetermined diameter. Alternatively, the use ofradiopaque inflation media to inflate the balloon can also permit invivo visualization.

Although the preferred embodiments described above rely upon the balloonto provide a visual reference, the objectives of the present inventionmay be accomplished using other visual indica which will permit theclinician to assess the relative in vivo inflation of the focal zone.Thus, in a broad sense, the invention contemplates a visualizable aspectassociated with the focal section and a visualizable reference indicasuch as the balloon, a radiopaque marker on or associated with theballoon, radiopaque inflation media, or others, which allows theclinician to compare the diameter of the focal section relative to someother visual reference.

In addition to the provision of a visual reference to allow theclinician to assess the inflated diameter of the balloon, the balloon ofthe present invention provides a way to focalize the balloon inflationenergy at a predetermined position along the balloon. The axial lengthof the focal section can be varied considerably, depending upon thedesired axial length along which inflation energy is to be focalized.For example, the axial length of the focal section may be anywherewithin the range of from about 0.5 cm to about 5.0 cm. For coronaryvascular applications, the axial length of the focal balloon willnormally be within the range of from about 0.5 cm to about 2.0 cm forperforming conventional PTCA. The axial length will normally be withinthe range of from about 0.5 cm to about 5 cm for implanting expandabletubular stents, depending upon the length of the desired stent.Normally, the axial length of the focal section will be greater than theaxial length of the stent.

A variety of focal balloon catheters of the present invention arepreferably available to the clinician having an array of different axialfocal lengths, so that a balloon having the appropriate focal length canbe selected at the time of the procedure based upon the nature of theprocedure to be performed, and the location in the vasculature. Forexample, in a curved portion of the artery, the clinician may wish tominimize the axial length of the focal zone to the extent possible whilestill having a sufficient axial length to accomplish the dilatation orstent implantation procedure. An excessive axial length in the inflatedballoon for a given curved vessel can elevate the risk of vasculardissection as is well known in the art.

The axial length of the reference zone can also be varied considerably,depending upon the desired performance characteristics. In general, ithas been found that axial lengths of at least about 3 mm allow readyvisualization by the clinician. Axial lengths much shorter than 3.0 mmmay require too much effort to observe under fluoroscopic conditions,and the reference function of the reference zone may thus not be readilyaccomplished.

In one embodiment of the invention, produced in accordance with thethree-zone illustration of FIG. 7, the proximal and distal referencezones each have an axial length of about 5.0 mm and an inflated diameterof about 3.0 mm at 8 ATM. The axial length of the focal zone, includingthe length of the second transition 76 and third transition 78, is about8 mm. The diameter of the focal zone at 8 atmospheres inflation pressureis about 3.5 mm.

The fixed focal balloon 64 can be manufactured using any of a variety oftechniques which will be understood to those of skill in the art. Forexample, the balloon can be manufactured by blowing suitable tubingstock into a stepped mold cavity. Alternatively, the tubing stock can beblown into a first mold having a diameter approximately equivalent tothe reference diameter. The balloon can then be blown into a second moldhaving a larger diameter section corresponding to the focal section inthe finished balloon. The balloon is inflated into the larger mold underthe application of heat, as will be understood by those of skill in theart.

The fixed focal balloon 64 of the present invention or other fixed focalballoons as described herein can be utilized in any of the methodsdescribed in connection with the differential compliance balloons of thepresent invention. Thus, the real-time diagnostic information about thelesion which is obtainable through the use of the focal or differentialcompliance balloons described in connection with FIGS. 1-6 herein canalso generally be achieved using the embodiment of FIG. 7. Unlessclearly specified to the contrary, the various methods of the presentinvention, including both the differential compliance and stentimplantation and sizing methods, are intended to be accomplished byeither the fixed focal balloon or the variable focal balloon embodimentsof the methods of the present invention.

FIG. 8-18 illustrate a variety of specialized focal and/or compliantzone balloons in accordance with the present invention. These balloonscan incorporate any of the structures, features, and methods of theprevious embodiments as may be desirable for particular intendedapplications. Therefore, construction techniques, materials, dimensions,capabilities and methodology discussed above applies to the followingembodiments, but will generally not be repeated below.

An alternate multi-zone balloon design of the present invention isschematically illustrated in FIGS. 8 and 9. Referring to FIG. 8, thereis disclosed a catheter having an elongate flexible tubular shaft 84such as has been discussed in connection with previous embodiments. Thecatheter shaft 84 is provided with a guidewire lumen 85 and at least oneinflation lumen 86. Guidewire lumen 85 terminates in a distal opening 87at the distal end 88 of the catheter.

A distal region on the catheter is provided with a balloon assembly 89.The balloon assembly 89 comprises an inner inflatable balloon 90disposed within an outer inflatable balloon 91. Inflation lumen 86provides fluid communication between a proximal source of inflationmedia (not shown) and the interior of the inner balloon 90. Theconstruction materials, construction techniques and dimensions of thevarious components of the various balloons and catheters illustrated inFIGS. 8 through 18 can be the same or similar to as those disclosed inconnection with previous embodiments. For example, the inner balloon 90may be constructed from a relatively noncompliant material such as PETor a relatively compliant material such as polyethylene.

The balloon assembly 89 is configured to produce a three zone balloon ofthe type that has been previously discussed, such that the balloonassembly 89 is inflatable first to a generally cylindrical configurationas illustrated in FIG. 8 and, thereafter, to a stepped configurationsuch as that illustrated in FIG. 9. Thus, a focal zone 92 (also referredto herein as a compliant zone) is disposed adjacent one or morereference zones, such as proximal reference zone 93 and distal referencezone 94.

In this embodiment, the inner balloon 90 and outer balloon 91 aredesigned to substantially maintain contact with each other, except inthe region of the focal section 92 once that section has focalized.Inner balloon 90 and outer balloon 91 may be maintained in contact attheir proximal and distal ends such as by the use of thermal bonding,adhesives, or other techniques described elsewhere herein. In addition,expansion limiting bands as have been previously discussed may also beincorporated into the balloons illustrated in FIGS. 8 and 9, such as inthe reference zones 93 and 94.

One feature which distinguishes the balloon illustrated in FIGS. 8 and 9from those previously discussed is the provision of one or moreapertures 95 for providing communication between the interior 96 ofballoon 90 and the interior 97 of outer balloon 91. Apertures 95 permita rate controlled diffusion of inflation media from the interior 96 ofballoon 90 into the space 97 to provide a delayed, gradual focalizationof the focal section 92. In use, the foregoing features permit theclinician to inflate the balloon assembly 89 to a preselected pressure,which will cause the balloon assembly 89 to inflate to its generallycylindrical inflation profile. Migration of inflation media through theports 95 then cause the compliant section 92 to gradually inflate to thesecond, stepped configuration of the balloon assembly as illustrated inFIG. 9.

Preferably, a plurality of discrete ports 95 is provided in the balloon90 to enable the diffusion of inflation media at a desired rate into thefocal section 92. The ports 95 are preferably each within the range offrom about 50 microns to about 400 microns across, and more preferablyare within the range of from about 100 to about 300. In one embodiment,the ports are about 250 microns in diameter. Depending upon the desiredrate of focalization, there are preferably anywhere from about 5 toabout 50 inflation ports 95 on the inner balloon 90. Alternatively, adifferent number of ports and/or port diameters can be used dependingupon the desired inflation characteristics of the balloon as a functionof time. The number and size of the inflation ports 95 thus can beoptimized for a particular desired inflation characteristic, taking intoaccount the viscosity of the inflation media at the temperature themedia is likely to be during an anticipated procedure.

In one embodiment, the outer balloon 91 comprises a relativelynoncompliant material, which is preformed into the second, steppedconfiguration. In this embodiment, a relatively high pressure can beintroduced into inner balloon 90. Inflation media will diffuse throughports 95 into the focal zone 92, thereby causing the balloon to assumeits second, stepped configuration substantially without actual expansionof the material of the focal section 92. Alternatively, at least thefocal zone 92 of the outer balloon 91 and preferably the entire balloon91 comprises a relatively compliant material as has been discussed, sothat the focal zone 92 grows by stretching in response to pressure asinflation media diffuses across inflation ports 95.

Referring to FIG. 10, there is illustrated a schematic outer profile ofa distally tapered balloon 100 which may be utilized in connection withany of the embodiments disclosed elsewhere herein. In general, the outerprofile comprises a focal zone 98, which may or may not be compliant.The focal zone 98 is adjacent at least one reference zone 99. In thisembodiment, the reference zone 99 is disposed proximally of the focalzone 98. A distal section 101 is provided on the balloon distally of thefocal section 98. Distal section 101 in the illustrated embodimentcomprises an elongate tapered section which reduces in cross-sectionalarea in the distal direction. As an alternate embodiment, distal section101 may comprise a generally cylindrical configuration, having across-sectional area in its inflated configuration which is smaller thanthe cross-sectional area of the proximal reference zone 99.

The above described modification to the exterior profile illustrated inFIG. 10 would thus produce a balloon having a configuration similar tothat illustrated in FIG. 3. However, the distal cylindrical section orreference zone has a diameter which is less than the proximalcylindrical reference zone. In general, the inflated diameter of thedistal reference zone will be no more than about 95% of the diameter ofthe proximal reference zone. Preferably, the inflated diameter of thedistal reference zone will be no more than about 80% of the inflateddiameter of the proximal reference zone. In one embodiment, the inflateddiameter of the distal reference zone is about 3.0, the inflatedfocalized diameter of the focal section is about 3.5 and the inflateddiameter of the proximal reference zone is about 3.25, at about 12atmospheres.

Both of the foregoing modified distal segment configurations take intoaccount the anatomical environment encountered during certaindilatations. For example, the native lumen in an artery on thecatheter's distal side of the lesion is often smaller in diameter thanthe native lumen on the catheter's proximal side of the lesion.Provision of a distal section 101 having a step reduction or a taperedreduction in the inflated diameter can permit the catheter to accomplishall of the desired functions, while at the same time reducing the riskof dissection of the artery. In addition, the tapered distal sectionsuch as the embodiment illustrated in FIG. 8 may facilitate treatment oflesions or implantation of stents in or adjacent a curved segment of theartery, as will be apparent to those of skill in the art in view of thedisclosure herein.

Referring to FIG. 11, there is disclosed a schematic illustration of atwo inflation lumen catheter for use with certain embodiments of theballoons of the present invention. The catheter 102 comprises aninflatable balloon assembly 103 at its distal end as has been discussed.The catheter 102 is further provided with a manifold 104 having aguidewire access port 105 in an over the wire embodiment. As has beendiscussed, rapid exchange embodiments may also be constructed in whichthe proximal guidewire access port 105 is located along the length ofthe catheter shaft 102, such as in the area of about 20 or 25centimeters proximally of the distal end of the catheter. In eitherembodiment, the distal end of the guidewire lumen typically exits thecatheter at a distal port 106.

The manifold 104 in this embodiment is provided with a first inflationport 107 and a second inflation port 108 for communicating with a firstinflation lumen 109 and a second inflation lumen 110, respectively.

Referring to FIG. 12, the first inflation lumen 109 is in fluidcommunication with the interior 112 of an inner balloon 114. The secondinflation lumen 110 is in fluid communication with the potential spacebetween the inner balloon 114 and an outer balloon 116. As has beenpreviously discussed, inflation of the inner balloon 114 will in mostembodiments cause the inner balloon 114 to assume a generallycylindrical inflated configuration. Inflation thereafter of the secondballoon 116 will cause the second balloon 116 to assume a focalizedconfiguration such as that illustrated in FIG. 13.

In an embodiment in which the outer balloon 116 is made from arelatively noncompliant material and preformed to have its steppedconfiguration, the outer balloon 116 need not necessarily be secured tothe inner balloon 114. Thus, a small space may exist in the inflatedconfiguration as illustrated in FIG. 13 between the outer balloon 116and the inner balloon 114 in the proximal and distal segments.Alternatively, as has been discussed, the inner and outer balloons maybe secured together in the proximal and distal zones, depending upon thedesired balloon construction materials and performance characteristics.

In an embodiment where the inner balloon 114 and outer balloon 116 aresecured together, a flow passage way 118 from the inflation lumen 110 tothe focal section 120 can be readily provided such as by insertion of amandril through the inflation lumen 110 and in between the balloons 114and 116 prior to the method step of securing the balloon together.Proximal withdrawal of the mandril (not illustrated) will thereafterproduce a flow passage way 118 as will be appreciated by those of skillin the art.

A variation of the embodiment of FIG. 13 is illustrated in FIG. 14. Inthis embodiment, a plurality of delivery ports 122 are illustrated inthe focal section 120 of the outer balloon 116. Delivery ports 122 willfacilitate the site specific delivery of substances to the vessel wall,such as drugs, or other diagnostic or therapeutic media as may bedesired. This embodiment of the present invention may be constructed andutilized in a variety of manners similar to those disclosed in U.S. Pat.No. 5,421,826 to Crocker, et al., the disclosure of which isincorporated herein by reference.

As has been referenced, supra, a multizone balloon including thetechnology of the present invention may desirably include a proximal anda distal focal or compliant section, and a central reduced diametersection. Two embodiments of the present invention incorporating thisfeature are illustrated in FIGS. 15 and 16.

Referring to FIG. 15, there is disclosed a dual-lobed balloon catheter130, comprising a single balloon 138 having a proximal lobe 140 and adistal lobe 142. By “single balloon” it is meant that the two or morelobes of the balloon may be inflated by way of a single inflation lumen.The actual balloon may comprise a single layer or a plurality of layers,depending upon the desired construction technique. For example, eitherone or each of the proximal lobe 140 and distal lobe 142 may have two ormore layers, expansion limiting bands, or other structures as disclosedelsewhere herein. A central zone of reduced inflated diameter 144 isdisposed between the proximal zone 140 and distal zone 142.

The balloon 138 is preferably mounted on an elongate flexible cathetershaft 132. Catheter shaft 132 is preferably provided with a guidewirelumen 134 and at least one additional lumen 136 such as for inflation ofthe balloon 138. Each of the proximal and distal lobes 140 and 142 mayhave any of the dimensions discussed in accordance with previousembodiments. In addition, either or both of the proximal and distallobes 140 and 142 may comprise a compliant construction or asubstantially noncompliant construction as has been discussed.

For example, balloon construction techniques disclosed previously hereincan be utilized to produce a dual-lobed balloon 138 in which theproximal lobe 140 and distal lobe 140 inflate to a diameter of, e.g.,about 2.5 millimeters at six atmospheres. As inflation pressure isincreased to, for example, 14 atmospheres, either or both of theproximal and distal lobes may be restrained from expanding beyond about2.6 or 2.7 millimeters. Alternatively, the proximal or the distal lobe140 or 142 or both may expand to as much as about 3.3 millimeters ormore at 14 atmospheres.

Selection of which of the proximal lobe 140 and distal lobe 142 to beexpandable to a greater inflated diameter will depend upon the intendeduse of the catheter. For example, in most coronary vascularapplications, the artery descends in diameter in the catheter distaldirection. Thus, it may be desirable for the proximal lobe 140 to beinflatable to a larger final diameter. Alternatively, applications ofthe balloon catheter 130 for such things as drug or other mediainfusion, heart valve replacement or repair, or other uses will requiredifferent dimensional relationships between the proximal lobe 140 anddistal lobe 142 as will be apparent to those of skill in the art in viewof the disclosure herein.

The central zone 144 can have an inflated diameter anywhere within therange of from about the outside diameter of the catheter shaft to about2.8 mm in a catheter for coronary vascular applications having aproximal balloon 140 with an inflated diameter of about threemillimeters. The diameter of central section 144 may be constrained suchas through the use of expansion limiting bands as has been discussed, orthrough the use of cross-linking techniques also discussed above.Alternatively, the central section 144 may be adhered to the cathetershaft 132, leaving only one or more axially extending flow paths forplacing the interior of lobe 140 in fluid communication with theinterior of lobe 142.

Referring to FIG. 16, the dual balloon counterpart to the designillustrated in FIG. 15 is disclosed. In general, dual balloon catheter148 comprises a proximal balloon 150, a distal balloon 152 and a centralzone 154 separating the proximal and distal balloons. The balloons aremounted on an elongate flexible catheter shaft 156. Catheter shaft 156is provided with a guidewire lumen 158, together with at least a firstand second inflation lumen 160 and 162. In the illustrated embodiment,inflation lumen 160 is in communication with proximal balloon 150 andinflation lumen 162 is in communication with distal balloon 152. Inother respects, the discussion in connection with the dual-lobed balloonof FIG. 15 is applicable to the dual balloon embodiment of FIG. 16. Ingeneral, the dual balloon embodiment permits slightly more flexibilityin terms of procedure, to the extent that it permits inflation of eitherthe proximal or the distal balloon first, followed by inflation of thesecond balloon where clinically desirable.

Referring to FIGS. 17 and 18, there is disclosed a therapeutic ordiagnostic agent delivery embodiment of the catheters illustrated inFIGS. 15 and 16. Referring to FIG. 17, there is illustrated a dual-lobeddelivery balloon catheter 170. The catheter 170 comprises a dual-lobedballoon having a proximal lobe 172, a distal lobe 174 and a central neckportion 176. An outer perforated or permeable layer 178 extends at leastfrom proximal lobe 172 to distal lobe 174 to entrap a space 180. Space180 is preferably annular, and is in communication with an infusionlumen 182 by way of one or more flow pathways 184. In one embodiment,outer layer 178 comprises an elongate tubular sleeve, which is neckeddown at the proximal end of proximal lobe 172 and also at the distal endof distal lobe 174.

The diameter of neck portion 176 is preferably at least somewhat smallerthan the diameter of proximal lobe 172 and distal lobe 174, to createspace 180 for the accumulation of delivery media. A neck portion 176which is inflatable to at least about 90% and preferably 95% or more ofthe diameter of adjacent lobes 172, 174 permits delivery of mediathrough the delivery zone yet minimizes the entrapped volume withinspace 180. The inflated diameter of neck 176 can be limited by any ofthe inflation limiting techniques discussed above, such as one or moreinflation limiting bands (not illustrated), cross linking, materialschoice, wall thickness variations, and the like.

The inflated diameter of neck region 176 may alternatively be as smallas permitted in view of the wall thickness of the balloon material, thewall thickness and diameter of the central guidewire lumen 184, plus thespace attributable to at least one flow passage 186 for communicatingbetween the proximal lobe 172 and distal lobe 174 of the balloon.

Outer layer 178 may comprise any of a variety of materials, such ascompliant or noncompliant materials well known in the drug delivery andballoon dilatation arts. For example, layer 178 may comprise PET,polyethylene, or other membrane materials well known in the art. Layer178 may be a permeable membrane, such that medication or other mediadiffuses therethrough. Alternatively, layer 178 is preferably providedwith a plurality of perforations 188 for permitting media to escape fromthe annular chamber 180 to the surrounding area.

The diameter and distribution of the perforations 188 can be modifieddepending upon the objective of the catheter, such as will be understoodby those of skill in the art in view of the disclosure herein. Forexample, provision of delivery perforations within the range of fromabout 100 microns to about 300 microns in diameter will permit a slowweeping expression of fluid media at low delivery pressures.Alternatively, reducing the cross-sectional area of the perforationsand/or increasing the delivery pressure can permit the media topenetrate through the elastic lamina layer and into the arterial wall.Port 188 diameter and distribution characteristics should also beselected taking into account the viscosity of any media to be delivered,and/or particle size if a particulate media is to be delivered.

One advantage of the configuration illustrated in FIGS. 17 and 18 is theability to isolate an arterial delivery zone in-between proximal lobe172 and distal lobe 174. Inflation of the dual lobes within an arterycan be accomplished at relatively low pressures to place the balloons incontact with the arterial wall. Infusion of media into annular chamber180 for expression through ports 188 may then be accomplished. Inflationpressure on the balloon can be increased, if an undesirably largequantity of media escapes downstream.

FIG. 18 is in all respects similar to FIG. 17 except for the use of twoseparately inflatable balloons. The details and operation of FIG. 18will be apparent to those of skill in the art in view of the discussionsin connection with FIGS. 15-17.

Either of the drug delivery designs of FIGS. 17 and 18 may alsoincorporate a perfusion conduit, for permitting perfusion past theinflated balloon during a drug delivery period. Perfusion conduits suchas those disclosed in U.S. Pat. No. 5,344,402 to Crocker, the disclosureof which is incorporated herein by reference, can be utilized.

Any of the hourglass type balloons of FIGS. 15-18 are particularly wellsuited for the implantation and/or sizing of vascular grafts. Forexample, an elongate tubular vascular graft can be positioned on thedistal end of the catheter of FIG. 15 and transluminally advanced to thetreatment site. As will be understood in the art, the treatment site maybe a portion of a vessel having an aneurysm or other wall defect whichis desirably spanned by the graft. The graft is preferably expanded bythe balloon to a first diameter at the treatment site. The proximal anddistal end zones of the graft are preferably expanded to a largerdiameter so that they are seated against the vessel wall proximally anddistally of the vessel wall defect. The balloon may then be deflated andwithdrawn. If the embodiment of FIG. 17 or 18 is used, the method mayadditionally include the step of expressing medication or other media atthe treatment site. The balloons of the present invention may also beutilized for methods of sizing an already implanted graft and/orinfusing medication or other media at the site of a previously implantedgraft by positioning the balloon within the implanted graft andrepeating the steps described above.

The present invention may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. The describedembodiments are to be considered in all respects only as illustrativeand not restrictive. The scope of the invention is, therefore, indicatedby the appended claims rather than the foregoing description. Allchanges which come within the meaning and range of equivalency of theclaims are to be embraced within their scope.

1. A balloon catheter, comprising: An elongate, flexible tubular bodyhaving proximal and distal ends; a first inflatable balloon on thedistal end of the tubular body; a first inflation lumen extendingthrough the tubular body and communicating with the first inflatableballoon; a second inflatable balloon surrounding at least a portion ofthe first inflatable balloon; a second inflation lumen extending throughthe tubular body and communicating with the second inflatable balloon;wherein the second inflatable balloon is inflated to a first inflationprofile by inflation of the first balloon, and the second balloon isinflatable to a second profile by inflation of the second balloon. 2-23.(canceled)